A. Field of the Invention
The device of the present invention generally relates to molded case circuit breakers, more particularly, to circuitry for controlling a solenoid used with a motor operator for changing from a remote location the operative condition of a molded case circuit breaker.
B. Description of the Prior Art
Circuit breakers and, more particularly molded case circuit breakers are old and well known in the prior art. Examples of such devices are disclosed in U.S. Pat. Nos. 2,186,251; 2,492,009; 3,239,638; 3,525,959; 3,590,325; 3,614,685; 3,775,713; 3,783,423; 3,805,199; 3,815,059; 3,863,042; 3,959,695; 4,077,015; 4,166,205; 4,258,403; and 4,295,025. In general, prior art molded case circuit breakers have been provided with movable contact arrangements and operating mechanisms designed to provide protection for an electrical circuit or system against electrical faults, specifically, electrical overload conditions, low level short circuit or fault current conditions, and, in some cases, high level short circuit or fault current conditions. Prior art devices have utilized an operating mechanism having a trip mechanism for operating the movement of an over-center toggle mechanism to separate a pair of electrical contacts upon an overload condition or upon a short circuit or fault current condition. Such trip mechanisms have included a bimetal movable in response to an overload condition to rotate a trip bar, resulting in the movement of the over-center toggle mechanism to open a pair of electrical circuit breaker contacts. Such prior art devices have also utilized an armature movable in response to the flow of short circuit or fault current to similarly rotate the trip bar to cause the pair of contacts to separate. At least some prior art devices use blow-apart contacts to rapidly interrupt the flow of high level short circuit or fault currents. The operating mechanisms of many prior art devices include a manually engageable handle for changing the operative condition of the circuit breakers. Often prior art devices have used a solenoid actuated motor operator for automatically changing the position of the handle from a remote location. The solenoid is energized from a source of electrical potential; and position sensing switches are often connected in series with the source of electrical potential to deenergize the solenoid after a switching operation of the circuit breaker has been completed. Typically, two position sensing switches are positioned at opposite ends of the mechanical travel of the handle or of the motor operator that moves the handle and are actuated when a switching action of the circuit breaker has been completed to terminate the flow of current to the solenoid.
Often, the adjustment of the position sensing switches is relatively critical, particularly in the case of circuit breakers having relatively short handle travel. If one or more of the position sensing switches are misadjusted or become misaligned to the point where it is not actuated at the completion of travel of the handle or motor operator, the solenoid could remain energized for an excessively long time and be damaged or destroyed.
While many prior art devices have provided adequate protection against fault conditions in an electrical circuit, a need exists for dimensionally small molded case circuit breakers capable of fast, effective and reliable operation and, more specifically, for circuit breakers that include solenoid control circuits for motor operators that reduce or eliminate the problems often encountered by the customary use of position sensing switches.